The ability to determine the presence of individuals relative to a location is often desirable. For instance, it may be desirable for subordinates to determine when their supervisor is in his or her office, e.g., so that they may speak with the supervisor. To locate their supervisor, subordinates may periodically walk past the office of the supervisor to determine whether he or she is in the office. While periodically checking the office of the supervisor is generally effective in allowing the presence of the supervisor to be determined, periodically checking the office may be relatively inefficient.
Rather than periodically checking the office of the supervisor to determine whether he or she is present, subordinates may instead attempt to contact the supervisor. By way of example, subordinates may e-mail or leave a telephone message for the supervisor requesting that the supervisor contact them when he or she arrives. However, the supervisor may not necessarily check his or her e-mail or telephone messages substantially immediately upon arrival at his or her office. Hence, the subordinates may not be aware of the presence of the supervisor in his or her office until relatively long after the supervisor has arrived.